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Remnant kidney hypermetabolism and progression of chronic renal failure
D C Harris1, L Chan, R W Schrier
1Department of Medicine, University of Colorado School of Medicine, Denver 80262.
Abstract:
To investigate the mechanisms whereby verapamil and dietary phosphate restriction slow progression of nephron loss after renal ablation, the effects of these maneuvers on inulin clearance (CIn), net sodium reabsorption (TNa+), oxygen consumption (QO2), and net glucose production (GP) were examined in isolated perfused normal and remnant kidneys. Preliminary studies characterized the isolated perfused remnant kidney perfusion. Adaptation to renal ablation was greater for QO2 (102% of normal), GP (138%), and kidney weight (79%) than CIn (51%) or TNa+ (40%). Verapamil (50 microM) lowered QO2 in remnant kidneys (1.64 +/- 0.24 vs. control 2.86 +/- 0.16 mumol.min-1.g-1, P less than 0.005), as did phosphate restriction (1.81 +/- 0.22 vs. control 3.05 +/- 0.40 mumol.min-1.g-1, P less than 0.05). These effects could not be accounted for by changes in CIn, TNa+, or GP and were not observed in normal kidneys. In summary 1) remnant kidneys are hypermetabolic compared with normal kidneys when assessed by QO2 and GP; 2) verapamil and phosphate restriction diminish the enhanced metabolic activity of remnant kidneys, an effect that is independent of TNa+; and thus 3) verapamil and phosphate restriction may slow progression of renal disease, at least in part by reducing renal metabolic demands.
Insights
Verapamil and phosphate restriction reduce the high metabolic activity in remnant kidneys. This reduction in renal metabolic demands may help slow the progression of kidney disease after renal ablation.
Area of Science:
- Nephrology
- Physiology
- Pharmacology
Background:
- Renal ablation leads to nephron loss and compensatory hypermetabolism in remaining kidney tissue.
- Understanding the mechanisms behind this hypermetabolism is crucial for developing interventions to slow disease progression.
Purpose of the Study:
- To investigate how verapamil and dietary phosphate restriction affect kidney function and metabolism after renal ablation.
- To determine if these interventions reduce the enhanced metabolic activity observed in remnant kidneys.
Main Methods:
- Utilized an isolated perfused remnant kidney model to assess inulin clearance (CIn), net sodium reabsorption (TNa+), oxygen consumption (QO2), and net glucose production (GP).
- Compared metabolic and functional parameters between normal and remnant kidneys.
- Administered verapamil (50 microM) and implemented dietary phosphate restriction to evaluate their effects on QO2 and GP.
Main Results:
- Remnant kidneys exhibited significantly higher oxygen consumption (QO2) and glucose production (GP) compared to normal kidneys, indicating hypermetabolism.
- Both verapamil and phosphate restriction markedly reduced QO2 in remnant kidneys.
- These metabolic reductions were independent of changes in CIn, TNa+, or GP and were not observed in normal kidneys.
Conclusions:
- Remnant kidneys are hypermetabolic, evidenced by increased QO2 and GP.
- Verapamil and phosphate restriction effectively diminish this enhanced metabolic activity in remnant kidneys.
- Reducing renal metabolic demands through these interventions may be a key mechanism for slowing the progression of kidney disease.